Anorthoclase(Na,K)AlSi3O8

Anorthoclase is another rare mineral species at MSH.

PHYSICAL CHARACTERISTICS:

Color is usually grey (mottled).Luster is vitreous to pearly on cleavage areas.Diaphaneity is transparent to translucent.Crystal System is triclinic; C.Crystal Habits include phenocrysts.Cleavage: {001} is perfect and {010} is good.Fracture is conchoidal to uneven.Hardness is 6 - 6.5Specific Gravity is approximately 2.6 g/cm3.Streak is white.Associated Minerals include (??).Distinguishing Features: Crystal habit.Origin: Named in 1885 from the Greek an, not, plus orthos, right, plus klan, to break, alluding to the fact that the cleavages are not at a right angle.